Electromyography as an aid in the prevention of excessive shoulder strain

Disorders in the musculo-skeletal system constitute the most common reasons for lowered working capacity and sick-leave in the engineering industry. The symptoms are often located in the neck-shoulder-arm and are greatly influenced by unfavourable muscle loads. A method for the routine study of muscular activity has been developed and tested for the purpose of reducing the risk of such work-related disorders. This method is based on the application of an electromyographic (EMG) technique and is primarily intended to facilitate the ergonomic assessment and the selection of alternative work postures. The tests performed confirm that EMG studies, in a simplified version for the shop-floor, may constitute a valuable aid for an objective analysis. They demonstrate that the EMG equipment used offers good possibilities to detect differences in muscle load in different work postures and that it meets the requirements for rapid presentation of the measured values, a simple analysis procedure, use on the shop-floor and simple handling.     

Effect of Carbon Content on Variant Pairing in Bainitic Low Alloy Steel

Metallurgical and Materials Transactions A - Variant pairing in bainite was evaluated in four different commercial low alloy steels with medium to high carbon content. The steels investigated were...     

Depolymerization of Turkish lignites. I. Effect of substituted phenols

A lignite (C, 67.4 wt%) was depolymerized with phenol, p-nitrophenol and o-chlorophenol using sulphuric acid as catalyst. The solubility of the lignite was enhanced by these treatments, with phenol being the most reactive reagent whereas p-nitrophenol was the least reactive. The distribution of nitro- and chloro-groups in the solubilized products was investigated by infrared spectrometry and it was found that these groups were redistributed among the pyridine- and methanol-soluble materials. It is suggested that benzene-soluble material is produced by self-depolymerization of coal or by degradation of pyridine- and methanol-soluble material.     

Molecular motion of small molecules in cellulose gels studied by NMR

Measurements of relaxation times, T₁ and T₂, and self-diffusion coefficients, D, for small molecules, viz., H₂O, dioxane and t-butanol, in the gel system cellulose/H₂O are reported and compared with those for H₂O in a polyacrylamide gel of the same polymer content. The temperature dependence of T₁ and D can for all the penetrants be represented by Arrhenius type relations which merely are parallel shifts by the same amount, towards smaller values, of those obtained without polymer. The T₂ values for H₂O in both gels pass through a shallow minimum over the considered temperature interval (14°?44°C). Furthermore, relaxation times T₁ of D₂O in the gel system cellulose/D₂O are reported; in a plot of ln T₁ vs. 1/T, a plateau region is observed at higher temperatures.     

碳四烷烃催化裂解制低碳烯烃的研究进展

论述了碳四烷烃催化裂解制低碳烯烃的催化剂体系、影响因素及催化裂解方式。该催化剂体系包括硅铝酸盐及锆硫酸盐,氧化铝与碱金属或碱土金属的混合物,负载型催化剂等3种类型。其中分子筛(晶体硅铝酸盐)及其改性催化剂是研究开发的主要方向。除操作条件外,稀释剂、引发和抑制剂和裂解反应方式对催化裂解反应均有影响。催化裂解反应机理与催化剂的种类和反应条件相关。对于酸性分子筛催化剂有2种比较公认的机理:正碳离子机理,自由基与正碳离子机理两种形式。研究表明碳四烷烃,特别是正丁烷催化裂解制低碳烯烃具有良好的低碳烯烃收率,收率可达50%以上。     

Boundary layer model for char combustion and gasification

A non-steady boundary layer model is developed for numerical simulation of combustion and gasification of a single shrinking char particle. The model considers mass and energy conservation coupled with heterogeneous char reactions producing CO and homogeneous oxidation of CO to CO₂ in the boundary layer surrounding the char particle. Mass conservation includes accumulation, molecular diffusion, Stefan flow and generation by chemical reaction. Energy conservation includes radiation transfer at the particle surface and heat accumulation within the particle. Simulation results predict experimentally measured conversion and temperature profiles of a burning Spherocarb particle in a laminar flow reactor. Effects of bulk oxygen concentration and particle size on the combustion process are addressed. Predicted particle temperature is significantly affected by boundary layer combustion of CO to CO₂. With increasing particle size, char gasification to char combustion ratio increases, resulting in decreasing particle temperature and increasing peak boundary layer temperature.     

Characterization and tests of planar Co3O4 model catalysts prepared by chemical vapor deposition

The chemical vapor deposition method was used to deposit thin films of cobalt oxide starting with cobalt (II) acetylacetonate and oxygen. The deposition process was investigated and the obtained films were identified as a cubic spinel-type polycrystalline Co₃O₄ with a crystallite size of 30–40 nm. The coating was carbon-free and the surface oxygen concentration was measured to be 66 at.% with AES analysis. Smooth and highly uniform thin films were deposited on planar stainless steel substrates and subjected to TPR and catalysis tests that show positive correlation. The apparent activation energy of Co₃O₄ reduction to CoO was measured to be (33±5) kJ/mol. The catalytic activity of Co₃O₄ was investigated toward the conversion of both propane and ethanol to carbon dioxide. Though the catalytic action was registered at the same temperature, the deactivation process was seen to be different. The catalytic conversion of ethanol induces a fast deactivation process, which was linked to its high ability to reduce Co₃O₄.     

The cholesterol-lowering effect of guar gum is not the result of a simple diversion of bile acids toward fecal excretion

The effects of partially hydrolyzed, nonviscous, guar gum (PHGG) on cholesterol metabolism and digestive balance have been compared with those of native guar gum (GUAR) in rats adapted to 0.4% cholesterol diets. Both types of guar gum elicited acidic fermentations in the large intestine, but only GUAR effectively lowered plasma cholesterol (P<0.001), chiefly in the triglyceride-rich lipoprotein fraction. The biliary bile acid excretion was significantly enhanced in rats fed GUAR (P<0.05), as well as the intestinal and cecal bile acid pool (P<0.001). In rats fed GUAR and to a lesser extent in those fed PHGG, the fecal excretion of bile acids and neutral sterol was higher than in controls (P<0.01). The digestive balance (cholesterol intake-steroid excretion) was positive in control rats (+47 μmol/d), whereas it was negative in rats fed GUAR (−20 μmol/d), which could involve a higher rate of endogenous cholesterol synthesis. In rats fed PHGG, the steroid balance remained slightly positive. Liver 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity was very low (22 pmol/min/mg protein), owing to cholesterol supplementation, in control rats or in rats fed PHGG, whereas it was markedly higher (+463%) in rats fed GUAR. In conclusion, even if PHGG does alter some parameters of the enterohepatic cycle of cholesterol and bile acids, its effects are not sufficient to elicit a significant cholesterol-lowering effect. The intestinal (ileal or cecal) reabsorption of bile acids was not reduced, but rather increased, by GUAR; nevertheless the intestinal capacities of reabsorption were overwhelmed by the enlargement of the digestive pool of bile acids. In the present model, induction of HMG-CoA reductase probably takes place in the presence of elevated portal bile acid concentrations.     

Additive manufacturing in the spare parts supply chain

As additive manufacturing (AM) evolves to become a common method of producing final parts, further study of this computer integrated technology is necessary. The purpose of this research is to evaluate the potential impact of additive manufacturing improvements on the configuration of spare parts supply chains. This goal has been accomplished through scenario modeling of a real-life spare parts supply chain in the aeronautics industry. The spare parts supply chain of the F-18 Super Hornet fighter jet was selected as the case study because the air-cooling ducts of the environmental control system are produced using AM technology. In total, four scenarios are investigated that vary the supply chain configurations and additive manufacturing machine specifications. The reference scenario is based on the spare parts supplier's current practice and the possible future decentralization of production and likely improvements in AM technology. Total operating cost, including downtime cost, is used to compare the scenarios. We found that using current AM technology, centralized production is clearly the preferable supply chain configuration in the case example. However, distributed spare parts production becomes practical as AM machines become less capital intensive, more autonomous and offer shorter production cycles. This investigation provides guidance for the development of additive manufacturing machines and their possible deployment in spare parts supply chains. This study contributes to the emerging literature on AM deployment in supply chains with a real-world case setting and scenario model illustrating the cost trade-offs and critical requirements for technology development.     

A new device for coating single particles under controlled conditions

A new device for coating a single levitated particle in a controllable environment is designed and tested. This enables fluidized bed processing to be simulated experimentally on a single-particle level. The device consists of a coating chamber, which contains a capillary tube for levitating the particle, a micro-dispenser for producing discrete drops of controlled size and velocity and a device for supplying gas with specified temperature and humidity. The coating chamber consists of two parts, a confined space where the particle is levitated and a droplet insertion cone where the coating solution is injected into the particle suspending gas flow. A capillary with a well-defined diameter connects the droplet insertion cone and the area where the particle is levitated. The device is equipped with a piezo-actuated flow-through micro-dispenser that has the ability to produce discrete droplets with high reproducibility in terms of droplet size and velocity. The gas required for the coating process is taken from a gas container where the water content is analysed and kept at a minimum. A liquid flow is then introduced into the gas flow at a well-defined flow rate, mixed and evaporated in a three-way mixing vault. The humidified gas flow is then split into two separate flows; a suspending gas flow and a protecting gas flow for the inside of the coating chamber. The device is equipped with a high-speed video camera for monitoring both droplet production and droplet impact. Temperatures and flow rates throughout the device are measured and logged. Preliminary results show the influence of solvent, gas quality and coating procedure on the quality of the coating.